Zwitterionic surfactants, i.e., those surface active compounds that contain both positive and negative charge centers in the same molecule while being electrically neutral, are well known and have been used in fabric laundering operations. Zwitterionic surfactants having alkylene oxide groups, and detergent compositions containing them, are also known. For example, U.S. Pat. No. 3,925,262 issued to Laughlin et al. on Dec. 9, 1975, discloses detergent compositions, which exhibit improved particulate soil removal performance, containing certain ethoxylated zwitterionic surfactants together with conventional detergent builder materials. Similarly, U.S. Pat. No. 3,929,678 issued to Laughlin et. al. on Dec. 30, 1975, discloses detergent compositions containing ethoxylated zwitterionic surfactants together with various cosurfactants for enhanced particulate soil removal. Zwitterionic surfactant compounds with a tetramethylene oxide moiety between the charge centers are disclosed in U.S. Pat. No. 4,159,277 issued to Gosselink et. al. on June 26, 1979. These compounds are combined with cosurfactants and builders, respectively, in U.S. Pat. No. 4,000,091 and U.S. Pat. No. 4,000,092, both issued to Wentler on Dec. 28, 1976. The pending application of Laughlin et. al. U.S. Ser. No. 849,745, filed Nov. 9, 1977 discloses certain zwitterionic compounds with alkyleneoxy groups for enhanced cleaning performance. Finally, U.S. Pat. No. 4,165,334, issued to Gosselink et. al. on Aug. 21, 1979 discloses ethoxylated sulfonium zwitterionic compounds and detergent compositions containing them. All of the above patents and the pending application are incorporated herein by reference.
While the zwitterionic surfactants disclosed above provide outstanding particulate soil removal performance, some even in the absence of builder materials, it would be desirable to improve their biodegradability in the environment. The present invention incorporates certain biodegradable chemical linkages between the cationic and anionic charge centers of alkyleneoxy zwitterionic compounds to make them readily biodegradable. It is to be understood that the placement of the linkage between the charge centers and anywhere from the second to the tenth atom from the cationic charge center is necessary to achieve the biodegradation advantages over compounds known in the prior art. Thus the compounds of the present invention provide both outstanding particulate soil removal performance and a high degree of biodegradability, and are therefore especially suitable for use in detergent compositions.